1. Field of the Invention
The invention relates to surgical clips used to occlude or ligate body tissues, such as blood vessels, lymphatic vessels and combinations of blood or lymphatic vessels imbedded in fat, muscle, fascia and visceral organs in surgical procedures both in conventional "open" operations and laparoscopic surgery.
2. Discussion of the Background
Traditionally, when ligation of vessels was required during surgery, one used "ties" (sutures alone) or stitches (sutures with a needle) to ligate divided blood vessels. With the increasingly popular laparoscopic surgery in which several small incisions are used to gain access to the abdominal cavity of the patient, it is much more difficult to use traditional tying or stitching (using sutures) to ligate vessels than in the classic "open" surgery in which a large incision is made in the patient.
Surgical clips, sometimes referred to as hemostatic or ligation clips are known, commercially available and an alternative to the use of sutures. These surgical clips are sold, for example, under the trade names Ligaclip and Hemoclip by Ethicon, Weck, and U.S Surgical. Essentially, Hemoclips or Ligaclips are the same and both occlude and ligate or close off blood and lymphatic vessels to prevent bleeding and lymph fluid leakage. In the present writing, the term "surgical clip" refers to a device to clamp and close-off (occlude and ligate) any type of tissues and/or vessels and will have applications which are the same or similar to the applications of both Hemoclips and Ligaclips.
FIG. 1 illustrates a conventional commercially available surgical clip such as the Ligaclip by Ethicon. This clip has a V-shaped configuration with legs 2 and 4 joined at an apex 6 which operates as a hinge. The legs 2 and 4 are spaced apart, usually at a 45.degree.-90.degree. angle from the hinge or apex. The conventional clip illustrated in FIG. 1 has a longitudinal groove and diagonal cuts on the clamping surface 8, a wedged-out section 10 for ease of bending, and protrusions 12 which provide a gripping surface for ease of application of the clip.
A common problem with conventional surgical clips is the slippage off the tissues or vessels. FIG. 2A illustrates a conventional clip having legs 2 and 4 enclosing tissue T in an unclamped state. FIG. 2B illustrates the conventional surgical clip in a clamped state around the tissue T. However, the configuration illustrated in FIG. 2b does not provide a very strong clamping force and the tissue T may slide or slip relative to the clip either longitudinally through the opening of the clip which is opposite to the apex or hinge 6 (i.e., the tissue slips off the legs of the clip), or slide transverse to the length of the clip (i.e., the clip slides along the length of the tissue). This means that the clip may slide horizontally or vertically of the intended occluded tissues. A test published in the article "How Secure Are Laparoscopically Placed Clips? An in Vitro and in Vivo Study" by M. T. Nelson et al, appearing in the publication "Archives of Surgery", Vol. 127, Jun. 19, 1992, determined that conventional commercially available surgical clips such as the Endo Clip or the Ligaclip are transversely (horizontally) dislodged with a mean force of 1.8-2.7 Newtons and axially or longitudinally (vertically) dislodged with a force of 4.0-4.8 Newtons.
In order to increase the security of surgical clips and prevent the clips from being dislodged, there have been numerous attempts to modify the shape/texture of the gripping surface of the clips in order to decrease the chances of the clip dislodgement. One such variation in the gripping surface of the clips is illustrated in FIGS. 3A and 3B in which a protrusion 20 is placed on one leg of the clip while a groove 22 is placed on the opposite leg of the clip. The unclamped and clamped states of such a clip are illustrated in FIGS. 3A and 3B respectively. Such a protrusion and groove structure can be seen in U.S. Pat. Nos. 4,976,722 and 600,887. Other variations of the gripping surface are shown in U.S. Pat. Nos. 4,799,481, 4,844,066, and 5,201,746. While these known alternatives to the gripping surfaces may improve the stability of surgical clips, the available surgical clips are still considered to be only marginally successful and often, two clips are used to provide added security to the occlusion of the vessel.